1. Field of the Invention
The present invention relates to a plastic optical fiber (hereinafter simply referred to as optical fiber) end surface processing method for processing a plastic optical fiber end surface into a convex or concave semi-spherical surface, a processing apparatus for the method, a cutter for use in the method, and an optical fiber connecting method for connection between optical fibers, connection between an optical fiber and an apparatus, and connection between an optical fiber and a connection device such as a connector, and, in particular, an optical fiber connection method which involves little optical loss at a connecting portion.
2. Description of the Related Art
Conventionally, when processing an optical fiber end surface into a spherical surface, heat is usually applied for end surface processing. For example, while maintaining an optical fiber in a vertical position, its forward end is heated by a high heat source such as a flame and liquefied, the end surface being formed into a convex semi-spherical end surface by surface tension. In this method, however, the heating is not conducted uniformly, so that the convex semi-spherical profile lacks reproducibility. Further, the end surface disadvantageously involves generation of flaws, adhesion of dirt, and the like.
In order to solve the above problems, there has been proposed an optical fiber end surface processing apparatus, which comprises, as shown in FIGS. 28A, 28B, 28C, and 28D, a fixing device (not shown) for fixing an optical fiber 21 having a predetermined length of an end portion exposed, a lens forming mold 53 which is heated at least when pressed against the forward end of the end portion of the optical fiber 21, a rapid cooling means 54 which is integrated with the lens forming mold 53 and moves with the same and which forcibly cools the end portion of the optical fiber 21 while the lens forming mold 53 is being pressed against the forward end of the optical fiber end portion or after the lens forming mold 53 is separated from the end portion of the optical fiber, and a conveying means (not shown) for pressing and separating the lens forming mold 53 and the rapid cooling means 54 against and from the forward end of the optical fiber end portion.
Further, in this optical fiber end surface processing apparatus, the optical fiber 21 whose end portion is exposed and which is equipped with a jacket 23 is fixed by a fixing device (not shown) (FIG. 28A); the lens forming mold 53 and the rapid cooling means 54 are pressed against the forward end of the optical fiber 21 by the conveying means (not shown) for heating to soften/melt a part of the end portion to form it into a lens profile (FIG. 28B); the end portion of the optical fiber 21 is forcibly cooled by the rapid cooling means 53 (FIG. 28C); and the mold 53 and the rapid cooling means 54 are separated from the forward end of the optical fiber 21 (FIG. 28D) to thereby obtain an optical fiber with a lens 55.
This apparatus makes it possible to form a lens (a semi-spherical surface) at the forward end of an optical fiber easily, efficiently and at low cost. It can form the convex surface with a satisfactory reproducibility, and advantageously hardly involves generation of flaws or adhesion of dirt.
However, while the above conventional optical fiber end surface processing apparatus utilizing heat is suitable for the formation of a convex semi-spherical surface, it is not applicable to the formation of other profiles such as a concave semi-spherical surface.